South Africa collapsed from a winning position to lose by 30 runs to West Indies in their T20 international on Sunday, with the Caribbean side taking an unassailable 2-0 lead in the three-match series.

West Indies made 179 for six but the South Africans were well on their way to victory, reaching 129 for 3 with more than six overs remaining.

The Proteas then proceeded to lose their last seven wickets for just 20 runs in 35 balls, finally ending up bowled out for 149.

Reeza Hendricks made 44 off 18 balls in a positive start to the run chase, but it was a day to remember for West Indies' seamers at the Brian Lara Cricket Academy Stadium.

Romario Shepherd took 3-15 from his four overs, claiming the key wickets of Hendricks and skipper Aiden Markram (19).

Fellow pacer Shamar Joseph took 3-31 as he did the damage to the lower order.

Shai Hope had set the home side on their way to a good total with his 41 from 22 balls while skipper Rovman Powell's 35 and Sherfane Rutherford's 29 saw them through the final overs.

Powell was pleased with the way his team had turned the game around after the strong start from the tourists.

"We put the pressure after the powerplay. Wickets would bring us back in the game. T20 cricket can change very fast," he said.

Markram said his experimental and youthful team would learn from the loss and seek to put it right in Tuesday's final game.

"It's tough to put a finger on the learnings right now but one thing guaranteed with us is a never-say-die attitude," he said.